The system employing an optically encoded digital audio disc (referred to hereafter as a compact disc) system, which is applied with an error correcting code of high correctability, can reproduce high-quality stereo music. If character data, still picture data and video game program data are recoded together with the stereo music data on the same compact disc in the same signal format employing the same error correcting code, it becomes possible to reproduce still pictures such as paintings corresponding to the reproduced music or to display the composer's name and the title of the music piece while the user enjoys the to reproduced stereo music, and also possible to reproduce suitable music for running video programs so as to expand the field of application of the present compact disc system. One prior-art compact disc has a data storage capacity of about 500 M bytes and thus can afford storage for both stereo musical data and digital data.
However, since many titles of present compact discs, on which only stereo musical data is recorded, have been already sold, it is preferable to ensure that any disc storing both digital stereo musical and other digital data as above-mentioned can be reproduced without any trouble with respect to the stereo musical data by prior art disc playback systems employed to playback prior art compact discs.
On the other hand, it is desirable to introduce a newly designed disc playback system which is able to playback both of the prior art compact discs and the discs storing two kinds of data as described above, or further able to reproduce discs storing only the other digital data. As regards the discs on which stereo music of same program is recorded, manufacturing the above kind of discs allows not only persons who own the conventional disc playback systems to enjoy high-quality stereo music as before, but also persons who will own new type disc playback systems which have display devices to enjoy both reproduction of stereo music and reproduction of still pictures.
Since the conventional disc playback system, however, aims at reproducing stereo music, when a disc storing digital data such as still picture data played by use of such systems, other than musical data is high level noises are generated so as to cause damage a loudspeaker and so on. Accordingly, the desired disc must prohibit prior art disc playback systems from audibly reproducing digital data other than stereo music. One method is to store the digital data in a pause section between one musical data and another musical data. However, this pause section is not necessarily mute but is sometimes treated as a fade-in and fade-out. Since prior art disc playback systems cannot hold the pause section mute, the pause section cannot store digital data.